Asphalt concrete is an important material used for road construction by combining asphalt, coarse aggregates, and fine aggregates.
In a general manufacturing process of the asphalt concrete, raw materials including aggregates, asphalt, a filler, and the like are mixed at a predetermined ratio, the materials stored in a cold bin are heated with a dryer through horizontal and inclined conveyor belts by adjusting a rpm of a feeder, separated for each standard by screens, and transferred to a hot bin.
However, in aggregates used for manufacturing the asphalt concrete in the related art, the amount of flat and elongated particles is too large and improvement thereof is required. Grades of the aggregates are calculated according to the amount of the flat and elongated particles, and when the amount of the flat and elongated particles is 10% or less, the aggregates are set and used as first grade and recommended in the spot. As the amount of the flat and elongated particles is decreased, a lifespan of the road is long and thus there is no need to frequently repair roads and as a result, traffic congestion may be avoided.
Herein, the used flat and elongated particles mean aggregates in which a ratio of a minimum length to a maximum length of the aggregate is more than ⅓ by using a measurer of the flat and elongated particles.
The aggregates occupying the most part of the entire volume of the asphalt concrete are a very important factor in the asphalt concrete due to a physically and mechanically large influence according to types and quality thereof. In the aggregates, crushed aggregates crushed from a rocky mountain having hardness and good durability exhibit excellent performance, but a supply shortage phenomenon is caused due to a recent sudden increase of construction works. In addition, treatment of waste asphalt concrete also becomes a major social problem. Accordingly, efforts to obtain recycled aggregates from the waste asphalt concrete to reuse the aggregates in manufacturing of the asphalt concrete have been increased.
Particularly, production of aggregates having uniform particle shapes from the coarse aggregates is an important factor of the asphalt concrete, but the amount of the flat and elongated particles has a large difference according to characteristics of the used equipment. In Korea, when the amount of the flat and elongated particles is 10% or less, most of the aggregates which are contributed and produced by set the first grade includes a large amount of flat and elongated particles.
Further, in order to use the recycled aggregates, added materials need to be more cautious and excellent physical properties are required.